Normal and various pathological conditions of a patient can be revealed by auscultation examination, listening for physiological sounds from the interior of the body, to determine the condition of the lungs, heart, arteries, veins, intestines, pleura and other organs. This examination is generally performed with an instrument called a stethoscope. A stethoscope examination is a fundamental medical examination procedure that is part of any routine examination performed by a physician. A stethoscope examination allows the physician to analyze a patient's cardiovascular and respiratory system. To perform this analysis, the doctor uses an acoustic stethoscope to listen to the sounds generated by the patient's cardiovascular and respiratory system. The typical examination involves a doctor placing a stethoscope bell-and-diaphragm chest piece on a patient's back or chest so that the doctor is able to listen to sounds at various locations on the patient's body. The bell acts as a filter to isolate sounds in a lower frequency range, while the diaphragm filters out lower frequencies and passes higher frequency stethoscope sound.
Although a stethoscope examination is a simple and routine procedure, it nevertheless requires that a patient be present with the doctor in an examination room. Consequently, those patients who may require frequent, perhaps even daily, stethoscope examinations are burdened by the administrative, financial, and logistical hardships involved in frequent visits to a doctor.
Patients who live a long distance from a doctor's office are particularly burdened. Patients residing in a remote location with a need to frequently see a doctor must either be admitted into a hospital (or other local facility), or be willing to hire a health care professional to visit or stay with the patient at the patient's home. For most patients, today's spiraling medical costs place both of these options out of reach. There exists a compelling need, therefore, for a system by which a doctor can perform medical examinations on a remotely-located patient while avoiding at least some of the usual administrative, financial, and logistical hardships.
Traditional stethoscopes have amplified and filtered sounds by acoustic means. Acoustic stethoscopes include a “chest piece” that is brought into contact with the patient's skin, and two flexible tubes, terminating in earpieces placed in the health care professional's ears. More recently, stethoscopes have been developed that use electronic amplification and filtering.
The use of various sensors that transform internal body sounds into electrical voltages is well known in the art. Various types of transducers have been used in implementing body sound sensors, including both air coupled and contact microphones and accelerometers. Combined acoustic and electronic stethoscopes are also known in the art.
Conventional acoustic stethoscopes generally operate in the range of about 10 Hz to about 1 kHz, while electronic stethoscopes generally have higher sensitivity and an extended high frequency range.
Modem systems for transmitting stethoscopic output over a telephone system have involved elaborate analog and digital processing steps in various attempts to compensate for the frequency characteristics of the telephone system. Exemplary analog processing steps include using the output of a stethoscope to modulate a carrier frequency that is within the bandwidth of a plain old telephone service (POTS) and shifting the frequency of the stethoscopic signal into the bandwidth of a POTS. Digital stethoscopic systems transmit a digital representation of the stethoscopic signal over the POTS or use the POTS to access a network, such as the Internet. All of the above systems have required additional equipment beyond the stethoscope and telephone at the remote site and specialized equipment at the diagnostic site.
There remains a need for a cost-effective stethoscopic system usable at different locations, for example, at a site remote from a health care professional.